Method and apparatus for producing a brazed plate heat exchanger block by sectional brazing

Abstract

A method and an apparatus for producing a block for a plate heat exchange is described wherein partition plates and heat-conducting structures are stacked together with brazing material in a block, and the block is subjected to a first force in the vertical direction. A first, upper section of the block is heated to a brazing-material softening temperature, and at the same time, a second section of the block is brought to a tempering temperature which is lower than the brazing-material softening temperature. Subsequently, the block is not subjected to any force from the outside or is subjected to a second force which is lower than the first force, and the second section of the block is brought to a brazing-material softening temperature. At the same time, the first section is brought to a tempering temperature which is lower than the brazing-material softening temperature.

The invention claimed is: 
     
       1. A method for producing a brazed block ( 11 ) for a plate heat exchanger ( 10 ), wherein the block ( 11 ) has a plurality of heat exchange passages ( 1 ) for indirect heat exchange between at least two fluids (A, B, C, D, E), and wherein a plurality of partition plates ( 4 ) and heat-conducting structures ( 2 ,  3 ) are stacked in a vertical direction (V) in the block ( 11 ), and brazing material ( 15 ) is disposed between adjacent partition plates ( 4 ) and heat-conducting structures ( 2 ,  3 ), said method comprising:
 (a) subjecting the block ( 11 ) in the vertical direction (V) to a first force (F 1 ) which acts on the block ( 11 ) from the outside, and heating a first, upper section ( 21 ) of the block ( 11 ) to a brazing-material softening temperature (T L ) at which the brazing material ( 15 ) softens, such that the upper section ( 21 ) is brazed, and wherein, at the same time, a second section ( 22 ) of the block ( 11 ), which adjoins the first section ( 21 ) downwardly in the vertical direction (V), is heated to a tempering temperature (T R ) which is lower than the brazing-material softening temperature (T L ) and above an ambient temperature and at which the brazing material ( 15 ) does not soften, and 
 (b) subsequently not subjecting the block ( 11 ) in the vertical direction (V) to any force from the outside or subjecting the block to a second force (F 2 ) which acts on the block ( 11 ) from the outside, wherein the second force (F 2 ) is lower than the first force (F 1 ), and heating the second section ( 22 ) of the block ( 11 ) to a brazing-material softening temperature (T L ) at which the brazing material ( 15 ) softens, such that the second section ( 22 ) is brazed, and wherein, at the same time, reducing the temperature of the first section ( 21 ) to a tempering temperature (T R ) which is lower than the brazing-material softening temperature (T L ) and above the ambient temperature and at which the brazing material ( 15 ) hardens or does not soften. 
 
     
     
       2. The method according to  claim 1 , wherein the first section ( 21 ) is formed by an upper half and the second section ( 22 ) by a lower half of the block ( 11 ). 
     
     
       3. The method according to  claim 1 , wherein the block ( 11 ) comprises a further, third section ( 23 ) which adjoins the second section ( 22 ) downwardly in the vertical direction (V), wherein, following (b), said method further comprises:
 (c) not subjecting the block to any force from the outside, and bringing the third section of the block ( 11 ) to a brazing-material softening temperature (T L ) at which the brazing material ( 15 ) softens, and, at the same time, bringing the second section ( 22 ) to a tempering temperature (T R ) which is lower than the brazing-material softening temperature and above the ambient temperature and at which the brazing material ( 15 ) hardens or does not soften. 
 
     
     
       4. The method according to  claim 3 , wherein the first section ( 21 ) is formed by an upper third of the block ( 11 ), and wherein the second section ( 22 ) is formed by a middle third of the block ( 11 ), and wherein the third section ( 23 ) is formed by a lower third of the block ( 11 ). 
     
     
       5. The method according to  claim 1 , wherein the first force (F 1 ) and the second force (F 2 ) are applied to the block ( 11 ) by means of at least one loaded spring ( 31 ,  32 ), wherein the at least one loaded spring ( 31 ,  32 ) acts from above on an outermost, upper partition plate ( 4 ) of the block. 
     
     
       6. The method according to  claim 1 , wherein, during the brazing of the first section ( 21 ) in step (a), the first force is applied to the block ( 11 ) by means of a first loaded spring ( 31 ) and a second loaded spring ( 32 ) and said first force is an aggregated force (F 1 ) corresponding to the sum of the forces exerted on the block ( 11 ) by the first loaded spring ( 31 ) and the second loaded spring ( 32 ), and wherein, during the brazing of the second section ( 22 ), the second force is applied to the block ( 11 ) only by means of the second loaded spring ( 32 ). 
     
     
       7. The method according to  claim 6 , wherein, following the brazing of the first section ( 21 ) in (a), the first spring ( 31 ) comes to bear against a first stop ( 33 ), such that the first spring ( 31 ) no longer acts on the block ( 11 ), and wherein, following the brazing of the second section ( 22 ), the second spring ( 32 ) comes to bear against a second stop ( 34 ), such that the second spring ( 32 ) no longer acts on the block ( 11 ). 
     
     
       8. The method according to  claim 1 , wherein the heat-conducting structures ( 2 ,  3 ) are formed by corrugated plates ( 2 ,  3 ). 
     
     
       9. The method according to  claim 1 , wherein, during the stacking of the partition plates ( 4 ) and heat-conducting structures ( 2 ,  3 ), edge strips ( 8 ) are arranged between adjacent partition plates ( 4 ), said edge strips ( 8 ) terminating each particular heat exchange passage ( 1 ) toward the outside. 
     
     
       10. The method according to  claim 1 , wherein the tempering temperature (T R ) is in a range from 5° C. to 150° C. below the brazing-material softening temperature (T L ). 
     
     
       11. The method according to  claim 1 , further comprising, following (a) and (b), welding at least one port ( 6 ) and/or at least one manifold ( 7 ) onto the block ( 11 ). 
     
     
       12. The method according to  claim 1 , wherein the tempering temperature (T R ) is 30° C. to 100° C. below the brazing-material softening temperature (T L ). 
     
     
       13. The method according to  claim 3 , wherein during (c) the first section ( 21 ) is also brought to a tempering temperature (T R ) which is lower than the brazing-material softening temperature and above the ambient temperature and at which the brazing material ( 15 ) hardens or does not soften. 
     
     
       14. An apparatus for producing a brazed block for a plate heat exchanger according to the method of  claim 1 , said apparatus comprising:
 a heating apparatus configured to heat the first section ( 21 ) of the block ( 11 ) to the brazing-material softening temperature (T L ) at which the brazing material ( 15 ) softens, and simultaneously heat second section ( 22 ) of the block ( 11 ) to a tempering temperature, 
 wherein said heating apparatus is also configured to subsequently heat the second section ( 22 ) to the brazing-material softening temperature (T L ) and bring the upper section ( 21 ) to a tempering temperature, which is lower than the brazing-material softening temperature, and above the ambient temperature, and
 a clamping apparatus ( 30 ) configured to subject the block ( 11 ) in the vertical direction (V) to the first force (F 1 ) acting on the block ( 11 ) from the outside, while the upper section ( 21 ) of the block ( 11 ) is heated to the brazing-material softening temperature (T L ), and to not subject the block ( 11 ) in the vertical direction (V) to any force from the outside or to subject the block to the second force (F 2 ), while the second section ( 22 ) of the block ( 11 ) is heated to the brazing-material softening temperature (T L ), wherein the second force (F 2 ) is lower than the first force (F 1 ).